As an automated manual transmission apparatus for a vehicle, such as an automobile, although it has been conventionally believed that a fluid-type torque converter can be generally applied, consideration should be given preferably to that a transmission efficiency for transmitting a driving force of a driving power source, such as an engine, may on occasions be deteriorated due to a slip in transmitting the driving force, the slip which tends to occur in the fluid-type torque converter. In the light of the foregoing, suggestions have given to an automatic operation of a transmission apparatus that is provided with a gear-type manual transmission. As one of examples thereof WO2003-532040A discloses a double clutch-type gearing and power transmission apparatus. FIGS. 8 to 11 illustrates an outline of this apparatus.
In the first place, a gearing and power transmission mechanism of this double clutch-type gearing and power transmission apparatus is explained with reference to FIGS. 8 and 9. In this gearing and power transmission mechanism, an output from a driving shaft 31, such as an output shaft of an engine, is transmitted to a first input shaft 33 through a first clutch 32a of a twin-clutch assembly (a double-clutch assembly) 32, and is further transmitted through a second clutch 32b of the twin-clutch assembly 32 to a second input shaft 34 which is of cylindrical-shaped and is coaxially arranged at an outer periphery of the first clutch 32a. As is summarized in FIG. 9, the first clutch 32a and the second clutch 32b are controlled in such a manner that a transmission torque A is increased while the other transmission torque B is decreasing, and vice versa, for example in general, in such a manner that the transmission torque A is controlled at a predetermined torque value TO when the other transmission torque B is controlled to be zero, and vice versa. This gearing and power transmission mechanism is further provided with a first intermediate shaft 35 and a second intermediate shaft 36, which are both arranged in parallel with the first input shaft 33 and the second input shaft 34. On the first input shaft 33, the first intermediate shaft 35 and the second intermediate shaft 36, a first gear transmission mechanism 30A is mounted, which is capable of establishing four shift stages: a first shift stage; a third shift stage; a fifth shift stage; and a seventh shift stage. On the second input shaft 34, the first intermediate shaft 35 and the second intermediate shaft 36, a second gear transmission mechanism 30B is mounted, which is capable of establishing three shift stages: a second shift stage; a fourth shift stage; and a sixth shift stage. On the first input shaft 33 and the second intermediate shaft 36, a rearward shift stage gear train 47 is mounted The first and second intermediate input shafts 35 and 36 are respectively linked to an output shaft 38 when a gear 48a, which is mounted on the first intermediate shaft 35, and a gear 48b, which is mounted on the second intermediate shaft 36, are respectively engaged with a gear 48c, which is mounted on the output shaft 38.
The first gear transmission mechanism 30A incorporates, therein, a first shift stage gear train 40, a third shift stage gear train 42, a fifth shift stage gear train 46 and a seventh shift stage gear train 44. The first shift stage gear train 40 is configured with a gear 40a, which is fixedly mounted on the first input shaft 33, and a gear 40b, which is rotatably mounted on the first intermediate shaft 35. The third shift stage gear train 42 is configured with a gear 42a, which is fixedly mounted on the first input shaft 33, and a gear 42b, which is rotatably mounted on the first intermediate shaft 35. A first switching clutch 50 is mounted on the first intermediate shaft 35, the first switching clutch 50 which is switched among three positions: a first shift stage position to be engaged with the gear 40b side; a third shift stage position to be engaged with the gear 42b side; and a neutral position not to be engaged with any of the gear 40b side and the gear 42b side. The fifth shift stage gear train 46 is configured with the gear 42a, which is fixedly mounted on the first input shaft 33, and a gear 46b which is rotatably mounted on the second intermediate shaft 36. That is, the gear 42a is shared by the third shift stage gear train 42 and the fifth shift stage gear train 46. The seventh shift stage gear train 44 is configured with a gear 44a, which is fixedly mounted on the first input shaft 33, and a gear 44b, which is rotatably mounted on the second intermediate shaft 36. A third switching clutch 52 is mounted on the second intermediate shaft 36, the third switching clutch 52 which is switched among three positions: a fifth shift stage position to be engaged with the gear 46b side; a seventh shift stage position to be engaged with the gear 44b side; and a neutral position not to be engaged with any of the gear 46b side and the gear 44b side.
The second gear transmission mechanism 30B incorporates, therein, a second shift stage gear train 41, a fourth shift stage gear train 43, and a sixth shift stage gear train 45. The second shift stage gear train 41 is configured with a gear 41a, which is fixedly mounted on the second input shaft 34, a gear 41b, which is rotatably mounted on the first intermediate shaft 35. The fourth shift stage gear train 43 is configured with a gear 43a, which is fixedly mounted on the second input shaft 34, and a gear 43b, which is rotatably mounted on the first intermediate shaft 35. A second switching clutch 51 is mounted on the first intermediate shaft 35, the second switching clutch 51 which is switched among three positions: a second shift stage position to be engaged with the gear 41b side, a fourth shift stage position to be engaged with the gear 43b side, and a neutral position not to be engaged with any of the gear 41b and the gear 43b. The sixth shift stage gear train 45 is configured with a gear 45a, which is fixedly mounted on the second input shaft 34, and a gear 45b, which is rotatably mounted on the second intermediate shaft 36. The rearward shift stage gear train 47 is configured with the gear 40a, which is fixedly mounted on the first input shaft 33, gears 47a and 47b, which both are fixedly mounted on a reverse shaft 37 that is arranged in parallel to the shafts 33, 34, 35 and 36, and a gear 47c which is rotatably mounted on the second intermediate shaft 36. That is, the gear 40a is shared by the first shift stage gear train 40 and by the rearward shift stage gear train 47. A fourth switching clutch 53 is mounted on the second intermediate shaft 36, the fourth switching clutch 53 which is switched among three positions: a sixth shift stage position to be engaged with the gear 45b side; the rearward shift stage position to be engaged with the gear 47c; and a neutral position not to be engaged with any of the gear 45b and the gear 47c. 
The first, second, third and fourth switching clutches 50, 51, 52 and 53 are automatically and selectively operated, by a controller (not illustrated), among the respectively three positions by use of the first and second clutches 32a and 32b, and first, second third and fourth shift forks 61A, 61B, 61C and 61D. The controller calculates, on the basis of a vehicle driving condition such as an accelerator opening degree, a vehicle speed and an engine rotational speed, a shift stage that is appropriate to the vehicle driving condition, and further controls each clutch 32a, 32b, 50, 51, 52 and 53 in such a manner of establishing the shift stage which is a result of the aforementioned calculation. Under a normal condition, the first and second clutches 32a and 32b are both controlled in such a manner that the respective transmission torque are increased and decreased contrarily to each other, as described above. On the other hand, when an engine is being inactivated, and a vehicle is not moving, the first and second clutches 32a and 32b are both released from being controlled.
Next, explained below is operation of the first gear transmission mechanism 30A and the second gear transmission mechanism 30B.
When the twin-clutch assembly 32 is not operated, both the first and second clutches 32a and 32b are released from being operated or engaged, and the clutches 50, 51, 52 and 53 are controlled to the neutral positions. When an engine, which is being connected to the drive shaft 31, is activated at a vehicle stationary condition, the controller shifts, by use of the first shift fork 61A, the first switching clutch 50 to the first shift stage position. The first clutch 32a is then engaged at an event that an engine rotational speed reaches a predetermined rotational speed in response to increase of an opening degree of a throttle valve. Accordingly, the driving torque of the drive shaft 31 is transmitted from the first clutch 32a to the output shaft 38 via the first input shaft 33, the first shift stage gear train 40, the first switching clutch 50, the first intermediate shift 35, the gear 48a, and the gear 48c, whereby a vehicle starts driving with the first shift stage established in the transmission. At this state, in the eventuality of shifting up to the second shift stage, the controller shifts, the second switching clutch 51 of the second gear transmission mechanism 30B to the second shift stage position, by use of the second shift fork 61B. In a matter of time, when a vehicle driving condition, such as an accelerator opening degree, a vehicle speed, and an engine rotational speed, becomes appropriate for driving at a second shift stage, the controller terminates engagement of the first clutch 32a and establishes engagement of the second clutch 32b. Accordingly, the driving torque of the drive shaft 31 is transmitted from the second clutch 32b to the output shaft 38 via the second input shaft 34, the second shift stage gear train 41 of the second gear transmission mechanism 30B, the second switching clutch 51, the first intermediate shaft 35, the gear 48a and the gear 48c, whereby a vehicle driving is switched from the first shift stage to the second shift stage. When an actual vehicle driving condition is appropriate for further continuously shifting up, the controller, by use of the first shift fork 61A, shifts the first switching clutch 50 from the first shift stage position to the third shift stage position. In a matter of time, when an actual vehicle driving condition becomes appropriate for driving at the third shift stage, the controller terminates engagement of the second clutch 32b and establishes engagement of the first clutch 32a, whereby shifting to a vehicle driving at the third shift stage.
As described above, when an actual vehicle driving condition becomes appropriate for further continuously shifting-up, the controller controls one of the switching clutches 50, 51, 52 and 53 in such a manner that a gear train of a shift stage, which is one shift stage lower than a shift stage being currently established in the transmission, is released from being engaged, and a gear train of a shift, stage, which is one shift stage higher than the shift stage being currently established in the transmission, is to be engaged. In a matter of time, when an actual vehicle driving condition becomes appropriate to a vehicle driving at the shift stage that is one shift stage higher, an engagement condition of the twin-clutch assembly 32 is switched. By repeatedly performing the above-described control in the transmission, a shift-up operation can be achieved. When an actual vehicle driving condition is appropriate for shifting down, the controller controls one of the switching clutches 50, 51, 52 and 53 in such a manner that the a gear train of a shift stage, which is one shift stage higher than a shift stage being currently established in the transmission, is released from being engaged, and a gear train of a shift stage, which is one shift stage lower than the shift stage being currently established in the transmission, is to be engaged. In a matter of time, when an actual vehicle driving condition becomes appropriate to a vehicle driving at the shift stage that is one shift stage lower, an engagement condition of the twin-clutch assembly 32 is switched. By repeatedly performing the above-described control in the transmission, a shift-down operation can be achieved. On the other hand, when a shift stage being currently established in the transmission is appropriate to an actual vehicle driving condition, the controller does not switch operations of the switching clutches 50, 51, 52 and 53, and of the first and second clutches 32a and 32b, and maintain the shift stage being currently established in the transmission.
In response to a manual reverse operation at a time that a vehicle is being stationary, the controller returns the first switching clutch 50 to the neutral position, as needed, and shifts the fourth switching clutch 53 to a rearward position. In a matter of time, when an engine rotational speed reaches a predetermined rotational speed in response to increase in a throttle opening degree, the first clutch 32a of the twin-clutch assembly 32 is engaged. Accordingly, the driving torque of the drive shaft 31 is transmitted from the first clutch 32a to the output shaft 38 via the first input shaft 33, the rearward gear train 47, the fourth switching clutch 53, the second intermediate shaft 36, the gear 48b and the gear 48c. 
Next, described below is an operation by the first and second gearing and power transmission mechanisms 30A and 30B with reference to FIG. 8. The shift forks 61A, 61B, 61C and 61D, which are respectively engaged with peripheral grooves that are defined circumferentially on outer peripheries of the switching clutches 50, 51, 52 and 53, are respectively linked to fork heads 60A, 60B, 60C and 60D (illustrated in FIGS. 10 and 11) via respective fork shafts (not illustrated) that extend in parallel with the shafts 33, 34, 35 and 36. The fork heads 60A to 60D are arranged in such a manner that tip ends of the respective fork heads 60A to 60D are lined up in a right-angled direction with the first and second input shafts 33 and 34. The tip end of each fork head 60A to 60D is integrally formed with a reverse-C shaped notch 60a. The reverse-C shaped notches 60a of the fork heads 60A to 60D are arranged so as to overlap one another in a direction, which makes right angles with the first and second input shafts 33 and 34. The fork heads 60A to 60D can be moved in a shift direction, which is in parallel with an extending direction of the input shafts 33 and 34, and can fall within a range limited by stoppers S1 and S2 that are provided at both sides of each fork head Therefore, in response to movement of one of the fork heads 60A to 60D, the corresponding one of the shift forks 61A to 61D can be operated via the corresponding fork shafts, and then the corresponding one of the switching clutches 50, 51, 52 and 53 can be switched to either a position at which the clutch is engaged with a gear at one side; a position at which the clutch is engaged with a gear at the other side; or a neutral position. The shift and select member 62 moves within the notches 60a in a select direction, which makes right angles with both the input shafts 33 and 34, and then selects one of the plural fork heads 60A to 60D. In such circumstances, at an event that the shift and select member 62 moves in the shift direction, the fork head, which has been selected, can be moved in the shift direction. Accordingly, the shift fork corresponding to this fork head is operated so as to switch the position of the corresponding switching clutch.
In the gearing and power transmission mechanism illustrated in FIG. 8, as described above, in the first place, a shift stage is established in the transmission by switching a gear engagement by use of the switching clutch 50 or 52 (or the switching clutch 51 or 53) of the gearing and power transmission mechanism 30A (or the gearing and power transmission mechanism 30B). In such a condition, in the eventuality of necessity of a shift operation, a next appropriate shift stage is selected by switching a gear engagement via the switching clutch 50 or 52 (or the switching clutch 51 or 53) of the gearing and power transmission mechanism 30A (or the gearing and power transmission mechanism 30B). As described above, wherever each fork head 60A to 60D is positioned, it is necessary that the shift and select member 62 positioned at a neutral position can be moved in the select direction. Therefore, as illustrated in FIG. 11(b), each notch 60a is designed to possess a dimension through which the shift and select member 62 can pass in the select direction wherever each fork head 60A to 60D is positioned among the one gear side; the other gear side; and the neutral position. Therefore, as illustrated in FIG. 10, a dimensional allowance D, which is superior to a shift stroke of each fork head 60A to 60D to one side, or is substantially equal thereto, is provided between one side of the shift and select member 62 at the neutral position (i.e., at an intermediate position) and one inner side of the notch 60a of each fork head 60A to 60D at the neutral position (i.e., at an intermediate position), and likewise between the other side of the shift and select member 62 and the other inner side of the notch 60a thereof.
Structures of the double clutch-type gearing and power transmission apparatus, and of the gearing and power transmission mechanism thereof, as is illustrated in FIGS. 8 to 11, are already described above.
According to the above-described conventional technology, each fork head 60A to 60D and each shift fork 61A to 61D can be held at the neutral position or at each shift position in an elastic manner by a detent device, which is configured with a ball, which is biased by a spring provided between each fork shaft (not illustrated) and a transmission casing, and plural notches elastically engaged with this ball. However, a member is not provided, which actively restrains each shift fork 61A to 61D at the neutral position, or each shift position. In this case, at a time that a strong external force is applied to each shift fork 61A to 61D, there is a danger of the shift fork of being undesirably displaced from the neutral position to one of the shift positions, or from one of the shift positions to the neutral position In this case, there is a danger of an occurrence of a gear jump out, in which a shift stage, which should actually be established in the transmission, can not be established, or of a double-gear engagement, in which a shift stage, which should not actually be established in the transmission, is undesirably established.
The present invention has been made in view of the above circumstances, and provides a twin clutch-type gearing and power transmission apparatus which is provided with an interlocking feature, by which, for example a gear jump out and a double gear engagement can be avoided.